It's not the typical sudden and complete cam lobe failure like we usually see these days, more of a long-term high-mileage thing. I've put at least 10k miles on this truck since I got it running and it's always run this way. It's a slight vibration/miss at idle that feels like a partially dead cylinder but doesn't make any bad noises. Vibration goes away once the throttle is open and the engine is spinning above idle, it's also less pronounced when the engine is fully warmed up.
IIRC I did a compression test a couple years ago and all cylinders were at acceptable levels relative to each other. I think the thin air makes it worse too combined with the low stock compression.
